HABscope: A tool for use by citizen scientists to facilitate early warning of respiratory irritation caused by toxic blooms of Karenia brevis

Abstract

Blooms of the toxic microalga Karenia brevis occur seasonally in Florida, Texas and other portions of the Gulf of Mexico. Brevetoxins produced during Karenia blooms can cause neurotoxic shellfish poisoning in humans, massive fish kills, and the death of marine mammals and birds. Brevetoxin-containing aerosols are an additional problem, having a severe impact on beachgoers, triggering coughing, eye and throat irritation in healthy individuals, and more serious respiratory distress in those with asthma or other breathing disorders. The blooms and associated aerosol impacts are patchy in nature, often affecting one beach but having no impact on an adjacent beach. To provide timely information to visitors about which beaches are low-risk, we developed HABscope; a low cost (~$400) microscope system that can be used in the field by citizen scientists with cell phones to enumerate K. brevis cell concentrations in the water along each beach. The HABscope system operates by capturing short videos of collected water samples and uploading them to a central server for rapid enumeration of K. brevis cells using calibrated recognition software. The HABscope has a detection threshold of about 100,000 cells, which is the point when respiratory risk becomes evident. Higher concentrations are reliably estimated up to 10 million cells L-1. When deployed by volunteer citizen scientists, the HABscope consistently distinguished low, medium, and high concentrations of cells in the water. The volunteers were able to collect data on most days during a severe bloom. This indicates that the HABscope can provide an effective capability to significantly increase the sampling coverage during Karenia brevis blooms.

Fig 1. The HABscope setup.

A photograph exhibiting the HABscope components, which are listed in Table 1 along with a list of suppliers and the 20 mL sampling vial.

Fig 2. Laboratory validation of HABscope cell counts.

A model validation of HABscope cell counts against varying concentrations of cultured Karenia brevis cells is shown. Cell concentrations determined with the HABscope (cells L^-1) are plotted against those determined with a particle counter (cells L^-1). The dashed line represents the 1:1 line.

Fig 3. Field validation of HABscope cell counts.

A plot showing the HABscope cell counts versus manually counted fixed cells from field-collected samples. The dashed line shows the 1:1 line.

Fig 4. HABscope field application data.

The results of the correlation between HABscope estimates of field samples taken by citizen scientist volunteers and cell counts of corresponding samples made by the authors are shown. Zero cell counts were set to 1000 so they could be plotted on a log scale. The green box at lower left shows concentration range for low respiratory risk range, the yellow box in the middle indicates medium-risk, and the red box (upper right) indicates concentrations associated with high-risk. The dashed line is the 1:1 relationship.

Fig 5. HABscope volunteer monitoring overview.

Results of HABscope volunteer monitoring on the west coast of Florida, USA over a 30 day period from 9-19-2018 to 10-19-2018. Each point corresponds to a single sample collected and color denotes Karenia brevis cell abundance as absent, low, medium, or high as shown in the figure legend. Y-axis is latitude with locations of the sampling sites marked and X-axis is date.